% \( ... \)
\((a ,b)=(1 ,2)\)  % one space between the comma and the following variable
\(( a+b ) * c = d(a ,b)\)  % no space between parentheses and variables
% $ ... $
$( a+b ) * c = d(a ,b)$    % no space between parentheses and variables
$a=1$  % one space before and one space after general binary operators
% \[ ... \]
\[( a+b ) * c = d\]  % no space between parentheses and variables
\[a + b\times  c = d\]  % \times is also an operator 
\[( a+b ) * c = d(a ,b)\]  % no space between parentheses and variables
% Suppose if I want to have line break after = operator
\begin{equation}
a^2+b^2=c^2
\end{equation}
